Process of making fat reduced spreads

ABSTRACT

A fat-reduced, edible, water-in-oil spread is produced by heating a fat which is normally solid at room temperature so as to melt a substantial proportion of less thermally stable crystals in the fat; homogeneously admixing sufficient water to the heated fat to reduce the proportion of fat in the resulting admixture; cooling the admixture to crystallize a substantial proportion of the uncrystallized fat and produce a pumpable plastic mass; and subjecting the pumpable plastic mass to cutting and mixing in a turbine-like comminuting device while limiting the temperature rise of the plastic mass.

This application is a continuation of 436,042 filed Nov. 13, 1989 whichis a continuation-in-part of application Ser. No. 184,186, filed Apr.21, 1988.

FIELD OF THE INVENTION

The present invention relates to improvements in the manufacture ofedible low-fat spreads.

BACKGROUND OF THE INVENTION

Conventional butter products contain about 80% fat, 15% water and 1.5%salt, and a mixture of minor amounts of other milk components that arecarried over into the butter during the churning process. The problemwith conventional butter products is essentially two-fold. First, theseproducts are highly concentrated forms of valuable butterfats, that insome cases are in short supply and in others can find productiveapplications other than in the form of conventional butter products.Secondly, while highly nutritional, butterfat belongs to a class offoods which are often in excess, at least in North American diets. As aconsequence of these factors there has been much interest in developingbutterfat or butterfat substitute products which are functionallyfungible with conventional butter products.

Much of the technological focus on low-fat butter or butter substitutedhas been on attempts to blend ever larger proportions of water intofat/water mixtures. The addition of water to fats in these mixturesinherently raises issues of emulsion instability, with it's associatedproblems becoming progressively more exacerbated in proportion to theincreasing amounts of water that are incorporated into the mixtures.

A case in point concerns attempts at forcing large amounts (i.e. about60%) of water into a 40% fat envelope, to produce a low-fat form of thegenerally preferred water in oil type emulsion. (This type of emulsionis preferred over oil in water emulsions because the kinestheticproperties of the latter are markedly dissimilar to butterscorresponding organoleptic properties. In addition, edible oil in wateremulsions have notoriously poor microbiological stability. Moreover, thephysical stability issues at low-fat concentrations in oil in wateremulsions are fundamentally different from the physical stability ofwater in oil emulsions, and the two are not at all comparable in theirbehavior in this regard). Although there is a substantial body ofliterature documenting the extensive efforts that have been expended ondealing with these instability problems, relatively little is knownbeyond the strictly empirical solutions that have been offered to date.According to the Encyclopedia of Chemical Technology: "Emulsiontechnology is at present based on a trial and error experience and aquasi-logical extension of that experience."

In general when the relative proportions of the continuous phase and thediscontinuous phase reach certain critical concentrations, the emulsiontends to destabilize. This is central to the problem faced in low-fatbutter products where the continuous fat phase is stretched to thelimits of it's ability to contain the relatively high proportions ofwater that are typical of these products.

Instability can manifest either as phase separation or phase reversal.When the relative concentrations of the phases approach theabove-mentioned critical conditions, it is necessary for othercharacteristics of the emulsion to augment the stability of the emulsionin order to meet commercial product specifications. In the case oflow-fat butter, those specifications call for a water in fat phaserelationship which resists phase separation (i.e. weeping, wheying-off,or bleeding). In general, the greater the resistance these products haveto phase separation the better, and the more closely the product willemulate butter.

The problem of instability has been addressed chemically. Threeapproaches have been tried: 1) alteration of the fat components throughaddition of other fats and/or refinement of certain butterfat species;2) addition of emulsifying agents, from both natural and commercialsources; 3) addition of stabilizing agents such as gums and gellingagents. All these approaches retard, to greater or lesser degrees, thecoalescence of the discontinuous phase of the emulsion.

The alteration of the fat components is aimed at increasing theviscosity of the emulsions continuous phase, by increasing the degree ofsaturation, or the average molecular weight, or both, and henceincreasing the average melting point temperature of the continuousphase. This solution has been employed commercially, but suffers fromthe fact that the changes in question change the plasticity of the fatsand modify the kinesthetic properties of the resulting products. Otherorganoleptic properties may also be adversely affected, especially inthe case where other fats such as vegetable fats are added.Additionally, market studies have shown a marked consumer resistance tothe addition of non-dairy fats. On the other hand, refinement of dairyfat components is a very expensive alternative and has not been widelyadopted.

The second of the above-mentioned approaches to stabilizing the emulsionchemically, involves the use of emulsifying agents. Broadly speaking,these agents include natural sources of emulsifying agents such, as forexample, non-fat milk solids and buttermilk. Caution must be exercisedin the use of these emulsifying agents since these are the same agentswhich normally support the oil in fat emulsions of milk and cream andmight therefore increase the risk of phase reversal when used in waterin fat emulsions. It is significant that buttermilk is separated outduring churning of conventional butter products. Other naturalemulsifiers include various soy fractions and the like, although thesessuffer from the disadvantage of not being indigenous to dairy products,and hence do not enjoy the "natural" connotation. Commercial emulsifyingagents include lecithin, various phospholipid preparations, surfaceactive agents ("detergents") and distilled mono and diglycerides. Strongcommercial emulsifying agents, however, have the potential to actuallydestabilize the emulsion by reducing the apparent viscosity. Moreover,North American marketing research attributes much of the lack ofcommercial success of products containing such agents, to consumerattitudes towards the use of "chemical" additives in foods.

The third approach involves the use of stabilizers to increase theviscosity of the water phase. Water-soluble gums and gelatins are usefulfor this purpose. Again, the addition of these agents is not wellreceived by consumers.

The instability of water in oil emulsions at high concentrations ofwater has also been addressed through mechanical emulsificationtreatments. In general, as the proportion of the dispersed phaserelative to the continuous phase increases, the viscosity of theemulsion also increases. In particular, when the volume of the dispersedphase exceeds the volume of the continuous phase, the emulsion particlesbecome crowded and the "apparent" viscosity of the emulsion takes on a"structural" component over and above the viscosity contributed by thecontinuous phase. In order for this structural viscosity to manifest inemulsions with high concentrations of a dispersed phase, the particlesize of the dispersed phase must be small enough to resist spontaneouscoalescence and emulsion destabilization. Mechanical emulsification isessential for these purposes.

The churn is one of the many devices that has been employed to this end,even if perhaps for no better reason that it's long association with thebutter industry. Bullock, J. Dairy Science, vol. 52, no. 5, 1969 foundthat serum and butter mixtures could be placed in plastic bags andtumbled in a churn. After one hour in the churn, these laboratory scalemixtures had formed water in oil emulsions with small, fairly welldistributed water droplets. The action of the churn depends for itseffect entirely upon so-called "turbulent mixing" in which turbulenceand diffusion result in both particle size reduction and dispersion ofthe discontinuous phase. While perhaps suitable for the processing oflow viscosity emulsions, such mixing is very inefficient when dealingwith more viscous emulsions (i.e. where viscosity is high enough tonegate mixing forces based of turbulence and diffusion alone). Note thata full hour was required to process even the very small test samplesdescribed in the Bullock reference.

A wide variety of emulsification equipment has been used with theobjective of breaking up or dispersing the discrete liquid phase in thefat phase so that the particles of the dispersed phase in the resultingemulsion are small and uniform enough to prevent coalescence andconsequential breakdown of the emulsion. This aspect of the emulsionsstability is most significant during post-emulsification handling of theproduct, and remains so until fat crystallization and thixotropic agingof the emulsion brings the product's stability up to its full potential.

In general, emulsification equipment is divided into two generalcategories: propeller emulsifiers and turbine emulsifiers. The Hobartmixer described by Bullock et al falls into the former category, andalthough that particular model is no longer commercially available itis, according to the manufacturer, equivalent to Hobart Model A-200T 20quart Mixer which operates a variety of agitators and beaters and thelike, at speeds of between about 100 and 400 rpm. This mixer producesboth dispersive and distributive forces, and relies primarily onturbulent mixing for this purpose. Stephan Machinery Corporationrecommends the use of its models UMM/SK and TC/SK type mixers forlow-fat spread applications. The UMM/SK and TC/SK type mixers areessentially multiple propeller type mixers having characteristics whichto some degree minimize the limitations imposed by simple turbulentmixing through the introduction of larger mechanical shear componentsinto the mixing process. See for example, U.S. Pat. No. 4,056,640.

Since turbulent mixing depends primarily on turbulence and diffusion,its usefulness as a standalone technique for producing fine emulsions issomewhat limited to the processing of low viscosity fluids, even though,in gross, the folding over of higher viscosity mixtures can be adequatefor some purposes, (as in the case of baking doughs, for example).Processes for producing fine emulsions of relatively high viscosityfluids, are known which involve the use of homogenizers and colloidmills. Both these devices has been classified as "modified" turbineemulsifiers, (see Encyclopedia of Chemical Technology, Volume 5, Page705) and both are known to be capable of producing high levels of fluidshear, as reflected by the associated mechanical heat rise duringprocessing.

In a homogenizer, emulsification is effected by forcing the two phasespast a spring-seated valve. This is usually done at relatively highpressures of 500 to 3000 psi. Emulsification occurs not only while thecomponents pass under the valve seat but also when the emulsion impingesagainst the retaining wall that surrounds the valve. As a general rule,homogenizers usually give an emulsion of finer average particle sizethan colloid mills, although the particle size is not as uniform.Possibly this is a reflection of greater dispersive forces at play inthe homogenizer, but that such processing is much more statistical (i.e.non-uniform). A mechanical temperature rise of about 10° F. to 30° F.(6° C. to 17° C.), is typical of homogenization processes, althoughdepending on the type of supply pump that is used, this may run as highas between 50° F. to 90° F.

In low-fat butter processing, it is generally acknowledged that highpressure treatments have a disadvantageous, destabilizing effect on theemulsion. In addition, lack of uniform processing in homogenizers mayleave a proportion of the dispersed phase in the form of particles whichare large enough to act as or promote the formation of coalescencenuclei either during subsequent processing or in the final product. Itis known, for example, that particles of different sizes coalesce moreeasily than do particles of the same size. Once such coalescent begins,it has the potential to destabilize significant amounts of the emulsionand result in weeping, etc.

Colloid mills on the other hand, produce the desired high degree ofuniformity of particle size without necessarily engendering the kinds ofoperating pressures associated with homogenizers. South African patentapplication number 86/2344, for example, cites line pressures of between80 and 116 psi, with pressure drops across the mechanical emulsifier inthe range of 22 to 58 psi. This mechanical emulsifier is speciallydesigned for the purpose of minimizing operating pressures. For thesereasons, much interest has been shown in their application in theproduction of low-fat butter products.

Unfortunately, colloid mills in general are known to result in very highmechanical temperature rises, on the order of between 30° F. to 140° F.(17° C. to 79° C.). The resulting high processing temperatures are knownto decrease the viscosity of the continuous phase of the emulsion andhave an adverse effect of its stability. In addition, although thedispersive forces generated in these devices produce highly uniformparticle sizes, they do not appear to produce corresponding levels ofdistributive forces. Without such distributive forces, inter-particledistances within the emulsion are not maximized and the more closelypacked particles of the discontinuous phase will have an increasedprobability of initiating coalescence, manifesting in grossdestabilization of the emulsion.

A series of South African patent applications assigned to Unilever,(including the above-mentioned South African patent application number86/2344), deal with a process in which a thermoplastics extruder isutilized for the purpose of producing low-fat butters and the like. Thedevice can be thought of as a modified colloid mill and is described indetail in U.S. Pat. No. 4,419,014. The device is intended to produce asmooth streamlined flow with limited substrate exposure to simple shearacross shear lands (for dispersive mixing) and laminar shear within thehemispherical cavities (to facilitate more uniform distributive mixing)over and above such turbulent mixing ("folding") as results when thesubstrate flow is repeatedly subdivided (across the shear lands) andrecombined during its transist through the device. According to theliterature, this arrangement is thought to reduce operatingback-pressures, as already noted herein, as well as reduce mechanicaltemperature rise and improve uniformity of processing by reducingproduct back flow within the device.

Notwithstanding this purported reduction in simple shear and increasedlaminar shear (and better distributive mixing) and even the supposedreduction in processing delta-t and more uniform substrate treatment,the process in question still requires temperature processing control.The use of an integrated heat exchanger apparently results in a moreuniformly dispersed emulsion, presumably because the fat phase issufficiently viscous at the reduced processing temperatures to retardpost-emulsification coalescence of the dispersed phase. One of theUnilever patents discloses that such temperature control is essential toproducing the homogeneity which is taught to be essential to thatprocess. Temperature control therein is affected by maintaining statorsurface temperatures of -20° C., in order to keep the average delta-t ofthe substrate within the range of 2° C. to 10° C.

There are a number of problems associated with this approach. First ofall, optimal fat crystallization is an extremely complexinterrelationship between endo and exothermic reactions within theprocessing milieu. External temperature control alters thethermodynamics of such processes on the microstructural level even whileattempting to compensate for the mechanical thermodynamic inputs ingross. This is a necessary consequence of heat transfer inertia into andwithin the substrate during processing even between the narrow annulusformed between the rotor and stator. This problem cannot be helped anyby the fact that in some embodiments the stator bears the temperaturecontrolled processing surface, even though the mechanical energy densityis highest along the rotor/substrate interface adjacent which thehighest substrate acceleration occurs. In any case, the microcrystallinestructure of the fat phase does not appear to be stabilized aseffectively as might be desired, through the use of such overt externalcooling. Consequently, even though South African patent applicationnumber 86/2344 indicates that margarine products produced using thisprocess can be packed as "cakes", there is no disclosure of any abilityto print products based solely on butterfat emulsions containing largeamounts of water, which is presumably a reflection of the latteremulsions (as produced in accordance with the application) inability tosurvive the rigors of the printing process.

SUMMARY OF THE INVENTION

In accordance with one aspect of the practices set out herein, there isprovided a process for producing edible water-in-oil emulsionscomprising the steps of:

a) subjecting a mixture of water-in-oil to a high degree of simple shearto disperse the discontinuous water phase by reducing the averageparticle size and particle size variance;

b) briefly subjecting the sheared mixture to mild post shearingturbulent mixing to distribute the discontinuous water phasesufficiently to increase the average interparticle distance and decreasethe variance thereof;

wherein the increase in the temperature due to shearing and mixing ofthe resultant water-in-oil emulsion is from about 1.5 Celsius degrees upto a temperature where the mixture becomes destabilized and substantialamounts of water are released from the water-in-oil mixture.

In accordance with a broad aspect of the present invention there isprovided a process for producing fat reduced edible water-in-fat spreadswherein the reduction in the amount of fat otherwise present is carriedout primarily through the addition of water as a finely dispersed phaseto an at least partially uncrystallized fat, the improvement in whichcomprises subjecting the resulting mixture to cutting and mixing in aturbine like comminuting device, wherein the increase in the temperaturein the mixture due to cutting and mixing thereof is from about 1.5Celsius degrees up to a temperature where the mixture becomesdestabilized and substantial amounts of water are released from thewater-in-oil mixture.

In accordance with a further aspect of the present invention there isprovided a process for producing a fat reduced edible water-in-oilspread of the type produced by dispersing water into an at leastpartially uncrystallized fat comprising the steps of:

a) substantially crystallizing the fat; and,

b) subjecting the resulting mixture to cutting and mixing in a turbinelike comminuting device;

wherein the increase in the temperature of the mixture due to cuttingand mixing thereof is from about 1.5 Celsius degrees up to a temperaturewhere the mixture becomes destabilized and substantial amounts of waterare released from the water-in-oil mixture.

Preferably the increase in the temperature of the mixture due to cuttingand mixing thereof is between 1.5 and 20 Celsius degrees; temperatureincreases of greater than 10 Celsius degrees can be tolerated if theproduct is to be packed in a tub, and preferably between 1.5 and 10Celsius degrees if the product is to be printed in known manner. It isespecially preferred that the increase in the temperature of the mixturedue to cutting and mixing thereof be between about 1.5 and 8 Celsiusdegrees. It is preferred that no active cooling be applied.

The edible fat is preferably selected from one of a group consisting ofbutterfat, margarine fats and mixtures thereof. Butterfat is preferablyselected from a source such as butter, renovated butter, or butter oil,or mixtures thereof, and butter itself preferably comprises about 80%milk fat, 16% moisture and about 2% milk solids not fat, and up to about2% salt.

Preferably sufficient water is dispersed into the at least partiallyuncrystallized fat so that the resulting mixture contains between 75%and 35% fat, and preferably between 30% and 50% fat as a proportion ofthe total weight of the mixture. Most preferred are low-fat mixturescontaining between 35% and 40% fat as a proportion of the total weightof the mixture. It is highly desirable that the water be homogeneouslydispersed in the substantially crystallized edible fat prior tosubjecting the mixture to cutting and mixing.

Preferably the mixture of water dispersed in the substantiallycrystallized edible fat has a temperature of from 13° C. to 17° C.(preferably 14.5° C. to 16.5° C. and especially preferably 14.5° C. to15.5° C.), and penetrometer values between 210 and 360.

It is preferred that following cutting and mixing the mixture has atemperature of between 15° C. and 18.5° C. (especially 15.5° C. and16.5° C.), and a penetrometer value of between 210 and 290, with valuesbetween 230 and 270 being especially preferred.

preferably the temperature rise in the mixture due to mixing along isabout 0.5 to 1 Celsius degrees.

The turbine like comminuting device preferably comprises an inlet forreceiving the mixture, the inlet being connected to a comminutingchamber housing at least one pair of mutually adjacent cutters eachbearing a plurality of blades with a plurality of passages formed therebetween, the cutters being arranged to be driven independently of anyflow of the mixture through the chamber, for relative mutual rotationwith respect to one another as nozzle and bucket, respectively, in aturbine arrangement, and through which the mixture can be passed. Uponpassage of the mixture through the blades the mixture is subdivided atthe passages formed between the blades of the nozzle cutter into aplurality of flows. On relative rotation of the cutters, the flows ofthe mixture are cut between the respective glades of the cutters, andthen passed on through the plurality of passages formed between theblades of the bucket cutter and subjected to mixing through therecombination of the plurality of flows, within a portion of the chamberadjacent an outlet therefrom, through which the mixture can exit thecomminuting apparatus.

preferably the comminuting device is a single stage turbine, andespecially a radial turbine, having concentric annular cutting rings.

The present invention also includes a process for producing fat reducededible water-in-fat spreads comprising the steps of:

a) heating a fat which is normally solid at room temperature, to belowthe heat of fusion of the most thermally stable crystals in the fat, fora period of time and to a temperature sufficient to melt a substantialproportion of less thermally stable crystals in the fat;

b) homogeneously admixing sufficient water to the heated fat to reducethe proportion of fat in the resulting mixture between 30% and 75% as aproportion of the total weight of the mixture;

c) cooling the admixture to crystallize a substantial proportion of theuncrystallized fat to increase the solids level and increase theviscosity of the admixture to produce a pumpable plastic mass;

d) subjecting the pumpable plastic mass to cutting and mixing in aturbine like comminuting device wherein the increase in the temperatureof the plastic mass due to the cutting and mixing thereof is from about1.5 Celsius degrees up to a temperature where the mixture becomesdestabilized and substantial amounts of water are released from thewater-in-oil mixture.

For the present purposes, fat-reduced spreads shall mean spreads having75% or less fat (as a proportion of the total weight of the mixture). Asused herein the term fat-reduced extends only to those products in whicha substantial proportion of the fat the would otherwise be present inthe product has been replaced through the addition of water. Inaccordance with one embodiment of the present invention, for example,such products contain between about 50 to 65% total solids. Low-fatspreads herein shall mean fat-reduced spreads containing (on the samebasis as aforesaid) between about 50 and 30% fat, and in particularthose having between 35 and 40% fat.

The present invention also relates to a process for producing fatreduced edible water-in-fat spreads wherein the reduction in the amountof fat otherwise present is carried out primarily through the additionof water as a finely dispersed phase, and wherein the improvementcomprises heating the additional water and a fat which is normally solidat room temperature to below the heat of fusion of the most thermallystable crystals in the fat, for a period of time and at a temperaturesufficient to melt a substantial proportion of less thermally stablecrystals in the fat and such that the remaining more thermally stablecrystals provide growth sites favouring the growth of more thermallystable species of fat crystals during subsequent fat crystallization,prior to mechanically subdividing the water therein to produce the finedispersion.

In accordance with another aspect of the processes of the presentinvention there is provided a process for producing a fat reduced ediblewater-in-fat spread wherein the reduction in the amount of fat otherwisepresent is carried out primarily through the addition of water as afinely dispersed phase to an at least partially uncrystallized fat, andin which the improvement comprises actively and uniformly cooling themixture from about 90° F. to 98° F. down to about 10° C. to 19° C. inabout 1 to 2 minutes, which conditions favour the growth of large,thermally stable fat crystals from sufficient of the partiallyuncrystallized fat, to produce a pumpable plastic mass prior tomechanically subdividing the water therein to produce a fine dispersion.

In addition to products produced in accordance with the practice of thepreceding processes, products per se are also included as aspects of thepresent invention. These include an uncomminuted intermediate useful inthe production of fat reduced spread, the intermediate comprising acrystallized, edible, pumpable plastic water-in-oil mixture having apenetrometer value in the range of 210 to 360 and a concurrenttemperature of between 13° C. and 17° C. (preferably 14.5° C. and 16.5°C. and especially 14.5° C. and 15.5° C.) as measured immediately priorto comminution thereof.

Also provided are comminuted intermediates useful in the production offat reduced spreads, which comminuted intermediate comprises an ediblewater-in-oil mixture having a penetrometer value in the range of 210 to290 and a concurrent temperature between 15.5° C. and 16.5° C. asmeasured immediately following comminution thereof and prior to anysubstantial post comminution crystallization. Preferably thepenetrometer value of the comminuted intermediate is between 230 and270.

The uncomminuted and comminuted intermediates preferably have a fatcontent of 75% or less, preferably between 30% and 75%. Especiallypreferred are low-fat intermediates having fat contents in the range of50% to 30% and particularly 35% to 40%.

The intermediates preferably have a total solids contents of between 65%and 45% as measured with the mixture equilibrated to room temperature.Non-fat solids contained in the mixture are preferably non-fat milksolids. The admixtures hereinabove preferably consist of buttermilk andbutter or buttermilk butter, and added water. Where buttermilk ispresent in the mixtures it is preferably derived from buttermilk, orcondensed or reconstituted buttermilk. These mixtures can furtherinclude minor, effective amounts of flavouring, colouring and ifdesired, preservatives. When butter is included in the admixture itpreferably comprises 80% butterfat, between 1% and 2% non-fat milksolids, and between 0% and 2% solids. Especially preferred are butterscomprising about 80% butterfat between 1.3% and 1.5% non-fat milk solidsand about 2% salt.

Buttermilk present in the admixture preferably comprises about 24% to33% total solids and 1.5% to 2% butterfat. A preferred admixturecomprises about 30% to 44% buttermilk, 0% to 22% added water, 45% to 68%butter and 0% to 1% added salt. These intermediates are especiallypreferred when they are low-fat spreads and the amount of added water isbetween 8% and 22%. Low-fat spreads containing between 45% to 47% butterare especially preferred. Total solids contents of 45% to 50% areespecially preferred in low-fat spreads.

Furthermore, the products according to the present invention extend tofat reduced edible spreads comprising a substantially crystallizedprintable, pumpable plastic water-in-oil mixture consisting of butterand buttermilk and having a fat content of 75% or less, and a totalsolids content of 45% to 65% at room temperature. Where necessary suchproducts can further include added water. Fat content of the ediblespread is preferably in the range of 75% to 30%, more preferably in therange of 50% to 30%, and especially preferably in the range of 40% to35%. A total solids content of between 45% and 50% is preferred. Inaddition, it is preferred that the buttermilk be condensed buttermilk.The mixture can also include minor effective amounts of flavouring,colouring and if desired preservatives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 4 of the drawings appended hereto illustrate variousviews and perspectives of a turbine comminutor especially suited to thepractice of the present invention.

FIG. 1 is a partial, longitudinal section through the comminutorapparatus.

FIG. 2 is a plan view in cross section through the comminutor chamberand cutting rings of the apparatus in FIG. 1.

FIG. 3 is an exploded perspective view of the comminutor housing andblade assembly of the apparatus depicted in FIG. 1.

FIG. 4 is a detail, exploded view of the blade assembly depicted in FIG.3.

FIG. 5 is a flow chart representing the processing stages and equipmentassociated therewith, as utilized in an especially preferred embodimentof the present invention.

FIGS. 6 and 7 are photomicrographs of mixtures formed pursuant topreconditioning mixing and pre-crystallization in the manner describedelsewhere herein.

FIG. 8 is a graphical representation in which penetrometer data isplotted against sample temperature for samples of product that have beenpreconditioned, mixed and pre-crystallized in the fashion describedelsewhere herein, and illustrates certain preferred processingconditions associated with "printability" of products of the presentinvention.

FIG. 9 is a photomicrograph of a product of the present inventionfollowing comminution thereof, but before the product is subjected toany substantial post comminution, handling or packaging. This is asample of the same material that is depicted, at an earlier processingstage, in FIG. 7.

FIG. 10 is a graphical representation in which penetrometer readings areplotted against the temperature of each post comminution sample ofproducts of the present invention, and showing preferred processingconditions and product characteristics associated with "printability".

FIGS. 11 and 122 are photomicrographs of samples taken immediatelyfollowing post comminution crystallization from the same production runthat was sampled for the purposes of FIGS. 7 and 9.

FIGS. 13 and 14 are photomicrographs of printed product produced fromthe same production run from which samples are shown in FIGS. 7, 9, 11and 12.

FIGS. 15 through 18 are photomicrographs of other "printed" products ofthe present invention.

DETAILED DESCRIPTION Fats

As used herein the terms oil and fat are to be construed synonymously,unless otherwise clearly indicated by the context. Products of thepresent invention are fat reduced and low-fat butters and margarine, andaccordingly fats useful in the preparation of such products areespecially preferred. Although butterfat is not the most inherentlystabilizing fat for use in producing low-fat or fat reduced mixtures, itis nevertheless the most desired fat from the consumers' standpoint.Suitable starting materials therefore include butter oil as well asbutter itself. Butter is sometimes defined as meaning the food productmade exclusively from milk or cream, or both, with or without additionalcoloring matter, and containing not less than 80 percent by weight ofmilk fat. A typical analysis of such products might show about 80percent milk fat, 16 percent moisture, less than about 1 percent curdand up to about 3 percent salt. For the purposes of the presentinvention, it is noted that butter obtained directly from the churningprocess is preferred from the standpoint of its inherent stability, overand above so-called process or renovated butter, which lacks theoriginal structure of the butterfat produced by the churning process.For the same reason, "butter oil" is also generally less preferred thanbutter obtained directly from the churn. Other fats useful in thepractice of the present invention are described in the Encyclopedia ofChemical Technology, Volume 8, The Interscience Encyclopedia, Inc., NewYork, pages 800 through 808.

The fat may be preconditioned by tailoring its crystalline structure toreduce the number of or even altogether remove unstable crystallineforms from the crystalline population at large, even though thisnecessarily means that without anything more, the overall proportion ofsolid fats is reduced. Preconditioning may be achieved, for example, byheating butter to between about 32° C. to 37° C. for a time sufficientto substantially reduce the amount of solid fats originally present inthe form of crystals having melting points at or below such temperaturesand to substantially eliminate those having lower melting points.Differential scanning calorimetry studies reveal that the crystallinepopulation of butter typically contains a substantial number of crystalsin a form having a melting point in the range 14° C. to 18° C., whichfor the purposes of the present invention are considered undesirable inthe early stages of the fat-reduced or low-fat spreads process. Thisspecific treatment si especially well suited for preconditioning ofbutterfat, but has application in the case of other fats as well, inthat the crystalline population of other fats so treated will then moreclosely emulate the kinesthetic properties that are associated withbutterfat at least in so far as having the organoleptic "melt"characteristics associated with butter is concerned. The treatment, ingeneral, preferentially leaves intact only those crystalline forms whichare associated with the desired stability and structure, both of whichare properties that play a significant role in subsequent processing offat-reduced and particularly low-fat spreads.

Water

As already stated hereinabove, the present invention relates to mixturesof water in oil. While the two substances are generally immiscible,solid fats will hold water suspended even though the mixture is not,strictly speaking, in the form of a mixture, provided however that thereis a sufficient excess of solid fats to do so. Thus, in conventionalbutter, fat is present in a sufficient excess and the mixture is stablefor all commercial purposes. At the other extreme, however, the largerrelative proportions of water in low-fat water-in-oil mixturesdestabilize the mixture unless the two are properly dispersed. Themoisture content of mixtures of the present invention need not beprovided as water per se, but can take the form of, for example, milk orbuttermilk. Thus water can be added by way of the addition of condensed,evaporated buttermilk. In this form, the added moisture includes suchthings as indigenous milk proteins, sugars, some additional butterfat,flavors and so on, each of which make their own contribution to thefinal product and in some cases affect processing too.

Other Ingredients

Water-in-oil mixtures of he present invention contain sufficient milksolids not fat, and or other indigenous dairy components having theability to stabilize any particular mixture under the selectedprocessing conditions to which it is subjected. The particular amountrequired in any case will be readily apparent to the person skilled inthe art, in light of the present disclosure and without undueexperimentation. Although none may be required to be added, and some maybe inherently present (as when butter is used as a source of butterfatfor example), the inclusion of such components is generally recommendedfor commercial production purposes.

Various sources of milk solids not fat may be used when required forthis purpose. A particularly preferred source of these components isbuttermilk, including buttermilk solids, condensed buttermilk,reconstituted buttermilk and the like.

Buttermilk that has been pasteurized is preferred, since this at leastpartially denatures indigenous whey proteins, exposing more hydrophobicsites on the protein molecules and reducing the tendency of suchproteins to favour phase reversal of water-in-oil mixtures. This permitsgreater advantage to be taken from any given amount of buttermilk, dueto the desirable phospholipids present therein.

In accordance with known practice in the art, various colors,preservatives and flavors (including salt which in the case ofconventional salted butter products actually serves both of the latterfunctions) etc. may be added. Note that nay such additives should firstbe evaluated for effects on mixture stability. Moreover, the fact thatthere is a lot more water, particularly in low-fat products, is a factorbearing on the amount and efficacy of such additives. In the case ofsalt, for example, the actual concentration in the water is much lowerin a low-fat product than an identical proportion (on a total weight ofproduct basis) of salt would be in a conventional butter product whereinthe quantity of salt is dispersed in far less water. This effects bothits favour contribution and preservative value.

Also, and especially where butter is concerned, there may be a marketdemand for purity and natural products. It is a feature of one aspect ofthe invention that non-dairy emulsifiers and stabilizers are avoided.However such substances may be used if desired.

Preliminary Mixing/Emulsification of a Water-in-Oil Mixture

The formation of an initial water-in-oil mixture includes the steps ofmixing the fat and water under conditions favoring the formation of awater-in-oil phase relationship, which conditions can be readilydetermined with a minimum of experimentation by a person skilled in therelevant arts in light of the present disclosure. By way of example,there is provided a process for emulsifying a mixture of water and oil,in the presence of emulsifying agents, wherein the water is heated to atemperature about equal to that of a melted fat. In addition tofacilitating the desired emulsification of the mixture, the preheatingof the water ensures that the thermodynamic processes entailed in theabovementioned tailoring of the fats crystal population are not undulydisrupted. The water is heated to between 32° C. and 37° C. (preferably33+ C. to 35° C.), consistent with the earlier described preconditioningof, especially, butterfat. Note that if the temperature of the mixtureexceeds about 37° C., then not only are the benefits associated withthermal tailoring of the fat crystal population lost but phase inversionalso can occur, and the thermal contribution of the water to the mixtureshould be adjusted to take this into account. The two are then admixedunder continuous agitation, by introducing water into the oil in amanner which at no time causes any local concentration of watersufficient to initiate phase inversion of the incipient emulsion. Slowrates of addition and sparging the water into the oil both assist inminimizing any localization of water at the outset of the emulsificationprocess. The dispersed phase can be divided and subdivided to a pointapproaching the limits of the indigenous and/or added, if any,emulsifying agents' ability to support the mixture (i.e. the emulsifyingagents' capacity to effect the increased interfacial surface area in themanner required to continue to stabilize that interface).

Precomminution Crystallization

According to U.S. Pat. No. 2,098,010, in connection with the manufactureof conventional oleomargarine products "coarse" emulsions, when passedthrough proper equipment for supercooling the fat, in the manner whichhas just been discussed, and then agitated while in a supercooledcondition, become further dispersed and a very fine emulsion is formed.We have found that milk or water emulsifies very readily and withextreme ease when agitated with fats which are in a supercooledcondition. The agitation of the fat in a supercooled condition causes avery fine dispersion of minute droplets of the dispersed phase of theemulsion. The supercooled product crystallizes or sets up so rapidlythat no opportunity is afforded for the coalescence of the finelydivided moisture and, consequently, no large droplets are formed. Thisresults in a very fine stable emulsion." On the other hand South Africanpatent applications 86/2341; 86/2343; 86/2344; and, 86/2342 disclose theuse of pre-crystallized fat prior to emulsification of a low-fatwater-in-oil emulsion. In connection with the present invention it hasbeen discovered that merely increasing solids through supercooling orpre-crystallization is not the answer, even though it may seem to followthat every increase in the viscosity of the continuous phase wouldnecessarily increase the apparent viscosity of the mixture and therebyimprove stability of the final product. It has now been found that,surprisingly, there is a criticality associated with thesupercooling/pre-crystallization of fats in the production of spreadswhich manifests in the type of structure in the final product connectedwith improving product stability and especially for printing fat-reducedand especially low-fat spreads, and in particular those based onbutterfat and containing only minimal amounts of indigenous dairyemulsifiers. The pre-crystallization process can be carried out byreducing the temperature of the previously described coarse mixture frombetween 32° C. to 37° C. down to about 10° C. to 19° C. in about one totwo minutes cooling time. The pre-crystallization can be accomplished oncommercially available crystallizers, typically operating at rates ofbetween 1800 to 4000 pounds of product per hour. In the Thermutatordevice described elsewhere herein the preferred throughput is about 2890pounds per hour for a one minute residense time and 1462 pounds per hourfor a two minute residence time.

Preferably treatment of the water-in-oil mixture by active cooling in acrystallizer is followed by passing the cooled mixture through arelatively larger diameter feed line to the comminutor device. Thus,while conventional 2" diameter pipes are used throughout the balance ofthe process, a 3" diameter pipe is used to connect theprecrystallization apparatus and the comminutor. The resulting pressureand friction reduction in this larger diameter line is consideredadvantageous. In addition this tube functions as a passivecrystallization device, much like a resting tube for example, and thetotal proportion of solid fat increases as the mixture passes therethrough. Note that there may be an attendant temperature rise inassociation with the release of heat from the mixture, since thecrystallization process is exothermic.

FIG. 8 of the drawings is a graphical representation of penetrometerdata plotted against product sample temperatures for low-fat productsproduced in accordance with a variety of the different processingconditions described herein. This figure illustrates the criticalityassociated with products which have proved to be most printable. Datapoints shown on the graph and which are subtended by the number "3" inbrackets were characterized as being excellent products from the pointof view of having both mixture stability and printable structure. Thosedata point subtended by the symbol "(1)" were not "printable" (on theSig Model FD100 printer set to produce and wrap 1 lb prints of product).

The products were produced using the process set out in FIG. 5, and thecomminuting apparatus depicted in FIGS. 1 to 4. The samples were inevery case drawn from the processing line connecting thepre-crystallizing apparatus and the comminutor, and the temperature andpenetrometer measurements were taken immediately. The penetrometerreadings are measures of the average distances in millimeters that aretraversed in each second by a free-falling 50 gram cone penetrometerfrom a starting point immediately above the flat surface of the sample,and measured over ten elapsed seconds. Preferably, the pre-crystallizedwater-in-oil mixtures give penetrometer readings of between 210 and 360,and have temperatures of greater than 14° C. and less than 17° C.(preferably 14.5° C. to 16.5° C. and especially 14.5° C. to 15.5° C.).

Referring to FIGS. 6 and 7 there is shown cryo-scanning electronmicrographs of two samples of the pre-crystallized mixture. Thesesamples were prepared by immersing portions thereof less than b 3 cubicmillimeters in volume, in liquid nitrogen slush at about -210° C., andfracturing the frozen samples to expose the surfaces to be viewed. Thesesteps were carried out in an EM Scope SP 2000 A cryoprepartion unit. Thesamples were then warmed to -80° C. for about ten minutes in order tosublime the surface water, then coated with gold and examined at -165°C. under an Hitachi S570 Scanning Electron Microscope equipped with acold stage. Note that even though the mixture as initially formed gavevisual evidence of good homogeneity of dispersion of the aqueous phase,FIGS. 6 and 7 illustrate large amorphous concentrations of water withinthe fat phases which can manifest as instability in the final product.

Comminution

The process of the present invention is especially advantageous when themixture has a high viscosity, (as for example in the case of a pumpableplastic mass), and when the edible spread is a low-fat product. In thecase of a high viscosity mixture, the relatively small increases intemperature result in correspondingly small reductions in viscosity. Asa consequence the viscosity of the continuous phase maintains asubstantial stabilizing influence on the mixture. Moreover, when thetemperature increase of a high viscosity mixture due to such processingis limited to within 1.5 Celsius degrees to 10 Celsius degrees, there isreason to believe that beneficial effects accrue in the crystallinemakeup of the fat phase. The dispersive and distributive mixing forcesstructure the mixture of water-in-oil in such a way as to increase thestability of the final mixture, as well as favourably influencing thetexture and structure of the resulting product.

The single stage shearing action is primarily a form of dispersivemixing, to comminute (subdivide) the water phase into small uniformparticle sized, without imparting too much energy to the system, whichwould diminish the stabilizing effects of the structure of thecontinuous phase and undo the effect and benefits of such dispersivemixing by allowing the dispersed aqueous phase to coalesce.

Mile post-shearing turbulent mixing is intended to distribute thedispersed particles within the continuous fat phase ideally so that theinter particle distance is a maximum, and the opportunity forcoalescence is thereby reduced.

Determining the balance between dispersive and distributive mixing is amatter within the routine skill in the art in light of the presentdisclosure. The temperature rise during processing that is attributableto mechanical shear and mixing is between 1.56 and 10 Celsius degrees.Preferably the temperature rise due to distributive mixing is about 0.5°C. Temperature compensation (active cooling) may be used if desired tomodify fat crystallization during processing in some particular way.

Apparatus useful for the purposes of comminution pursuant to the presentinvention include the Ytron Z in line single and multiple stage turbinecomminutor manufactured by Dr. Karg GMBH, Daimierstrasse 2, D-7151Affalterbach. Also useful in the practice of the present invention isthe Urschel Comitrol processor model 1700 equipped with a "microcuthead" (Urschel Laboratories Inc., 2530 Calumet Avenue, P.O. Box 2200,Valparaiso, Ind., U.S.A.). An especially preferred apparatus useful inthe practice of the present invention is the Stephan "Microcut" ModelComminutors. Model MC15 is described in detail in relation to thepreferred embodiment as set out hereinbelow.

Referring now to FIG. 10 of the drawings, there is depicted a graphicalrepresentation showing the same kind of relationships already describedin relation to FIG. 8, between penetrometer readings and temperature,but in the case of FIG. 9, for samples taken immediately aftercomminution. Products most suited for printing exit the comminutor atgreater than 15° C. and less than about 18.5° C. and preferably between16.5° C. and 15.5° C. The penetrometer readings are preferably between210 and 290, especially 230 to 270.

FIG. 9 of the drawings shows an electron micrograph of the sample ofcomminuted water-in-oil product taken immediately following comminution.The figure clearly illustrates the substantial improvement in dispersionand distribution of the aqueous phase resulting from the comminutionprocess. The sample in question was produced in accordance with theprocess outlined in FIG. 5, using the comminutor apparatus shown inFIGS. 1 to 4. Pre-crystallization was carried out at about 13° C. andthe comminution was operated at about 2,963 rpm, with a producttemperature rise across the comminutor of about 7 centigrade degrees.

Post comminution Handling and Packaging

Control of back pressure following comminution, and during the handlingand packaging of the fat reduced and especially low-fat spread productsdescribed herein, has been found to be significant in avoidingirreversible damage to the product's stability. Minimizing line pressureis highly desirable, although some allowance must be made for the typeof packaging equipment being used. In the case of products to be packedin tube, such back pressures can be readily minimized, as will beapparent to the person skilled in the art in light of the presentdisclosure.

Where the product is to be printed however, consideration must be givenboth to post comminution crystallization effects, and minimum operatingpressures required for commercial printing apparatus. In order toaccommodate such a crystallization process, the comminuted productshould be subjected to a resting stage in known manner sufficient toprovide a degree of fat crystallization suitable for surviving therigors of the particular printing apparatus. The duration of the restingstage and the amount of shear and especially back pressure to which thecomminuted product is subjected can be readily determined empiricallywith a minimum of experimentation by a person skilled in the art, inlight of the present disclosure.

With regard to necessary operating back pressures in the supply line tocommercial printing apparatus, the applicants have found that linepressures of between 10 and 65 psi are preferred. The lower limit ofthis range is based on the minimum supply pressure necessary to operatea Benhil Miltipack 8380 butter printer. Another commercial printingapparatus, the Sig Model F100 printer requires somewhat higher linepressure feeds, and will accommodate only lower delta-t products fromthe comminutor (preferably about 2° C.). Accordingly the Sig Printer isless preferred. Other commercial packing machines include by way ofexample Gerstenberg Block Packer VHA/VFA, HFR and PFR-K all of which areavailable from Gerstenberg and Agger A/S, Denmark. Printing ispreferably carried out at product temperatures of less than 68° F.

Pressure

Line pressure compensation and control can be achieved in known mannerin the art. A particularly preferred compensator is the Sig standardpneumatic compensator (used in conventional oleomergarine productionlines) described in detail elsewhere herein. Other compensators includefor example, Gerstenberg type 32 and type 40 compensators, althoughthese latter two are high pressure compensators and their high pressurecapacity may not be required for the purposes described herein. Theapplicants have also found that use of a slightly heated (to keepproduct flowing evenly) 30' to 40' length of 2" pipe open at the exitthereof and connected to the processing line intermediate between thecomminutor and the printer, can also provide suitable back pressurecontrol. The selection of apparatus for use in back pressure controlwill depend on the amount of back pressure required to meet the supplyrequirements for the particular printer apparatus.

PREFERRED EMBODIMENT

In accordance with a preferred aspect of the present invention there isprovided a process for producing a printable low-fat butter productcomprising a combination of butter and buttermilk. Unless otherwiseexpressly provided, reference numerals used in this part of thespecification will be to FIG. 5.

In accordance with that process, butter obtained from Ault FoodsLimited, Laverlocher, comprising 80% fat, 1.5% solids not fat and 1.9%salt was taken from a refrigerator at 7° C. and passed directly at 10°C. into a Benz & Hilgers GMBH Butter Reworker (Typ 8477, Bauj 1979,Auftrag 477/21), 1. The butter was processed at a residence time of 1.44seconds per kilogram. The Reworker includes a steam jacketed chute atthe outlet thereof. The butter is deposited as blocks at the inlet ofthe Reworker, and is captured by the flights of twin extruder screws,passed through the machine under pressure and partially melted thereinby the time it reached the exit chute. The exit chute is heated to atemperature sufficient to further melt the butter, but is primarilyintended merely to keep the butter flowing smoothly and cleanly exitingfrom the Reworker. The temperature of the butter exiting the Reworker isabout 14° C. the butter is then passed into a Cherry Burrell RoundProcessor Model WTC, 2. This device is described in general in U.S. Pat.No. 2,144,713 and 2,371,807. The butter is heated to between 32° C. and37° C. and preferably between 32° C. and 35° C., then held for mixing.

A preferred buttermilk useful in the practice of the present inventionis available from Ault Foods Limited at Laverlochere, Quebec. Thebuttermilk comprises a maximum fat level of about 1.7% and total solidsranging between 21% and 23%. The product has a maximum titratableacidity of about 0.12% as measured at 9% total solids. The buttermilk isobtained from cream which does not contain any whey cream, and is freeof any neutralizer residues. The buttermilk is held below 7° C. prior toprocessing. It is preheated to a temperature of 92° C. for a holdingtime of about 170 seconds and then passed into a falling film evaporatoruntil the desired solids level is achieved. The product is then cooledto less than 4.4° C. and has a sweet clean flavour.

The buttermilk is introduced into a Cherry Burrell Composition Controlunit model WTS, 3. This apparatus is described in detail in U.S. Pat.Nos. 2,144,713, 2,371,807, and 2,536,297. Water is added to thebuttermilk in order to standardize the water content of the finalbuttermilk/butter admixture, including butter, to 10.6% milk solids notfat.

The standardized buttermilk is then pasteurized under agitation at 18rpm in the side swept composition unit, by raising the temperature ofthe buttermilk to 71° C. for 30 minutes. Following pasteurization thetemperature of the standardized buttermilk is reduced to between 32 and37 and preferably between 32° C. and 35° C.

The standardized, pasteurized buttermilk is then pumped through a CherryBurrell Model A Pump, 4, at a rate of about 110 pounds to 120 pounds perminute into a sparger device, 5, located beneath the surface of themelted butter held in the Cherry Burrell Round Processor Model WTC, 2.The sparger, 5, is a 25/8" diameter spherical stainless steel sprayballmounted on a 1" inside diameter threaded stainless steel 11/2" longinlet fitting. The sparger ball includes 62, 1/16" diameter holes in thehemisphere thereof, opposite the inlet fitting. The buttermilk andmelted butter are then admixed over a period of between 15 and 20minutes and under constant agitation in the Round Processor, 2, run at48 rpm.

A preferred formulation of the present invention results in theadmixture of butter having about 80% fat, 1.5% solids not fat and 1.9%salt, with condensed buttermilk having a total solids of about 34.22%,2.15% fat, 32.07% solids not fat and about 65.78% moisture, togetherwith sufficient additional water, to produce a final compositioncomprising about 381/2"% fat, 10.6% milk solids not fat, 1.5% salt,50.6% total solids and 49.4% moisture. The preferred product containsabout 389 calories per gram, as compared with regular commercial butterat about 725 calories per 100 grams.

Once the mixing is complete, and a stable, coarse water-in-oil mixturehas been formed, the mixture is delivered through an APV Crepaco Pump,6, size R3R powered by a Sterling Model 88D, 1.5 horse power, 60 to 300rpm motor with a 9.3 gear ratio operating off a Sterling Speedtrol at arate sufficient to keep a downstream positive pump supplied at a linepressure of between 8 and 15 psi. The temperature of the mixture iswithin the range of 36° C. to 37° C.

The mixture is thus supplied to a Gaulin Homogenizer, 7, with variablespeed drive. The homogenizer, 7, has been modified through the removalof the homogenizer valves and valve seats. In this configuration thehomogenizer, 7, operates only as a positive displacement pump. The pumpis designed to operate in the range of 1800 to 4000 pounds per hour, ispreferably operated at about 2400 pounds per hour (18.2 kilograms perminute). this results in a line pressure of between 42 to 160 psiimmediately downstream of the homogenizer, 7. The higher line pressurevalues are associated with high solids, usually fat-reduced, products.In the production of low-fat butter products, line pressures are moretypically in the range of 40 to 60 or 70 psi. The temperature of themixture exiting the homogenizer is in the range of 33° C. to 35° C.Mixture is pumped under pressure to a Cherry Burrell Thermutator Model672, 8. The residence time within the Thermutator, 8, with the equipmentoperating at 2400 pounds per hour, is about 1.2 minutes. In themanufacture of low-fat products, only one leg of the Thermutator, 8, isused to achieve pre-crystallization of the butterfat. In the highersolids embodiments, both legs, with longer residence times must be usedto achieve the same degree of pre-crystallization. The residence time ina single leg of this apparatus is about 1.2 minutes with a rate ofthrough put of 2400 lbs/hr. the temperature of the product exiting theCherry Burrell Thermutator, 8, is about 10.5° C. to 19° C. The mixtureis passed into a resting tube comprising a length of three inch diametertubing, of sufficient length for the product, to reside therein forabout 60 seconds at a through put of about 2400 lbs/hr. The productundergoes an increase in temperature of between about one and one-halfof 1° C. as a result of loss of latent heat of crystallization duringthe product's residence in this tube, 9. Upon exiting the tube, 9, thetemperature of the pre-crystallized mixture is between about 11° C. and20° C. (preferably 13° C. to 15° C.; and especially 13.5° C. to 14.5°C.), and the line pressure is between 25 and 110 psi. Again, the higherline pressures are associated with high solids, i.e. fat reducedproducts. In the case of low-fat products, the line pressure ispreferably between 25 and 65 psi.

Comminution

The pre-crystallized mixture is then passed to a comminutor device, 10.A preferred comminutor apparatus is the Stephan Microcut, model MC15,Comminutor.

Referring now to FIG. 1 of the drawings, there is depicted a view takenthrough a portion of a preferred comminuting apparatus associated withthe present invention. The apparatus comprises a base and motor housing,1, arranged to support a comminutor housing, 2, containing a comminutingblade assembly, 3. The blade assembly is rotatable about a drive shaft,4, connected and driven relation to a motor, not shown, located withinthe base and motor housing, 1. Product enters the comminutor housingfrom above, and travels downwardly therethrough, through the cutterassembly, 3, and is finally passed outwardly through outlet 5. FIG. 2 ofthe drawings is a cross section in plan view taken through lines A andA-prime of FIG. 1. FIG. 2 depicts the relationship between thecomminutor housing, 2, and the rotor, 6, and stator, 7, of the cutterarrangement, 3. Product travels downwardly through the comminutorhousing, 2, into the interior of the rotor, 6. Product is then forcedoutwardly through gaps, 6a, between the blades, 6b, of the rotor, 6,where the product is sheared between the leading edge of blades 6a andthe stationary faces of blades 7a adjacent gaps 7c formed between blades7a and spacer element 7b in the stator 7. The comminuted product passesthrough the paths, 7c, into a comminutor housing manifold, 18. Finallythe product flows under distributive mixing conditions to outlet 5.

FIG. 3 of the drawings illustrates in an exploded perspective view thecomminutor housing 2, shaft 3, and a bearing assembly, 9. Stator 7 isdepicted with blade rings 7a and spacers 7b assembled. Also shown as anoptional helical screw 10 for facilitating the supply of product to theinside surfaces of stator 6.

Referring now to FIG. 4 of the drawings, there is shown an exploded viewin detail of the blade assembly 3 depicting rotor 6, and an explodedview of stator 7 illustrating in detail, blade ring 7a and spacer ring7b. The inside diameter of stator ring 7, as assembled, is 125 mm. Theassembled stator includes 20 gaps therein, each of which are about 0.05mm wide by 25 mm high. The rotor 6 includes 19 angled teeth spaced 9 mmapart from one another. Each such tooth has a slant height of 25 mm andthe length of the carbide cutting face 11 is 11 mm.

In operation, using the preferred water-in-oil formulation describedhereinabove at a through put of 2400 lbs thereof per hour thecomminuting device described hereinabove resulted in product temperatureincreases as shown below in Table 1.

                  TABLE 1                                                         ______________________________________                                                           Temperature Rise                                           Operating Speed (rpm)                                                                            (In Celsius Degrees)                                       ______________________________________                                          0                less than 1                                                1320               greater than 1                                             2140               about 4                                                    2960               about 7                                                    3570               about 11                                                   ______________________________________                                    

EXAMPLE 1

In accordance with the preferred practice of the present invention AultFoods Limited buttermilk from Laverlochere, containing 25.11% totalsolids, 2.05% fat was standardized by admixing 319.68 kilograms of thebuttermilk with 218.56 kilograms of water in order to standardize themixture to 8.7% milk solids not fat in the final mixture. This admixturewas pasteurized at 82° C. for thirty minutes and processed in the CherryBurrell Composition Control Unit Model WTS at 18 rpm. 4.4 Kilograms ofsalt were added to the admixture.

Ault Foods Limited butter from its Laverlochere facility, containingabout 80% fat, 1.28% solids not fat and 1.9% salt was processed in abutter reworker to a temperature of about 14° C. About 440.26 kilogramsof this butter was passed into a Cherry Burrell Round Processor ModelWTC. The temperature of the butter was raised to between 32° C. and 37°C. and the butter was mixed with the buttermilk (also at the sametemperature) in the manner hereinbefore described using a sparging balland agitating the admixture at 48 rpm. Mixing time was about fifteen totwenty minutes. The resulting 982.91 kilograms of admixture contained45.87% total solids and 36.5% butterfat. The mixture contained somelarge droplets of the aqueous disperse phase. The mixture was thenpumped from the Cherry Burrell Round Processor at 34.5° C. and 15 psi tothe already described Gaulin Homogenizer. The through put of theHomogenizer was set to 2447 pounds per hour and the post-homogenizerline pressure was between 40 psig and 70 psig. The mixture was thenpassed to a Cherry Burrell Thermutator whereafter about 1.2 minutesresidence time it exited at about 14° C. Post-crystallization linepressures were between 35 psi and 60 psi. The partially crystallizedmixture was then passed to the Stephan Comminutor operating at about1320 rpm. The mixture exited the Comminutor at 15.5° C. at a linepressure of 15 psig to 30 psig. The product was then printed in onepound blocks using the Sig Model F100 printer.

EXAMPLE 2

In this example 439.21 kilograms of buttermilk obtained from Ault FoodsLimited Laverlochere facility and comprising 24.77% total solids, and1.8% fat, were admixed with 87.51 kilograms of water. The mixture waspasteurized at 71° C. for thirty minutes in a Cherry Burrell CompositionControl Unit Model WTS. 6.09 Kilograms of salt were added to theadmixture.

475 Kilograms of butter, substantially as described hereinabove inrelation to Example 1, was passed at about 14° C. from a butter reworkerinto a Cherry Burrell Round Processor Model WTC. The butter was heatedto between 32° C. and 37° C. and admixed with buttermilk held at thesame temperature in the manner already described herein., The totalweight of the admixture was 1007.82 kilograms, and contained 50.60%total solids, 38.5% butterfat and 1.5% salt. The resulting mixture wasobserved to be smooth and creamy with a high degree of homogeneity. Theadmixture was then pumped at about 35° C. and 14 psig to 18 psig to theaforementioned Gaulin Homogenizer. The Homogenizer delivered 2400 poundsper hour of the admixture, at 45 psig to 55 psig, to a Cherry BurrellThermutator. After about a one minute residence time in the Thermutatorthe temperature of the mixture had been reduced to between 13.7° and14.3° centigrade. This product was delivered at between 40 psig and 50psig to the Stephen Comminutor. The Comminutor was operated at 1320 rpm,and product exited the Comminutor at about 16.5° C. and 15 psig to 30psig, which pressure was maintained using known compensator apparatus.The product was passed to a Sig Model F100 printer and printed in onepound blocks. The resulting product was a high quality product withglossy surface.

EXAMPLE 3

325.33 Kilograms of buttermilk, sourced as hereinbefore described inrelation to Examples 1 and 2, containing 33.74% total solids, 2.7% fat,was admixed with 203.37 kilograms of water. The admixture waspasteurized at 71° C. for thirty minutes in a Cherry Burrell CompositionControl Unit Model WTS. 6.12 Kilograms of salt were added to theadmixture in the Composition Control Unit.

475 Kilograms of butter, substantially as described hereinbefore inrelation to Examples 1 and 2, was passed through a butter reworker, andexited at about 14° C. into a Cherry Burrell Round Processor Model WTC.The buttermilk and butter were admixed substantially in the manneralready described to produce a final admixture of 1009.83 kilogramshaving 50.6% total solids and 38.5% butterfat and 1.5% salt. The mixturewas of good quality, well dispersed mixture.

The mixture was pumped at 34.5° C. and 10 psi to 12 psi to the GaulinHomogenizer. The Homogenizer was operated at 40 psi to 70 psi with athrough put of 2407 pounds per hour of mixture. The mixture was thenpassed to the Cherry Burrell Thermutator where after 1.2 minutesresidence time the temperature was reduced to 13.8° C. The linetemperature between the pre-crystallization apparatus and the StephanComminutor was 35 psi to 65 psi. The Stephan Comminutor was run at 1320rpm, and the product exited the Comminutor at about 15.9° -C. and 15psig to 25 psig. The resulting product was printed using a Sig ModelF100 printer, as one pound blocks. The product was of good quality.

EXAMPLE 4

439.41 kilograms of buttermilk containing 24.38% total solids, 1.5% fatwas admixed with 84.9 kilograms of water and pasteurized for thirtyminutes at 71° C. in a Cherry Burrell Composition Control Unit ModelWTX. 6.06 Kilograms of salt were added to this admixture.

475 Kilograms of Ault Foods Limited butter obtained from Laverlochereand comprising 80.1% fat, 1.50% solids not fat and 1.9% salt were workedin a butter reworker to a temperature of 14° -C., and then passed to aCherry Burrell Round Processor Model WTC. The butter was then heated tobetween 32° C. and 37° C. and admixed substantially in the same manneralready described hereinabove, with the buttermilk to produce 1005.37kilograms, a mixture having 50.71% total solids and 38.5% butterfat and1.5% salt. The mixture was characterized as being very stable anduniform mixture. The mixture was then pumped at 10 psi and 35°centigrade to the Gaulin Homogenizer. The Homogenizer delivered themixture at 2400 pounds per hour and a line pressure of 45 psi to 55 psito the Cherry Burrell Thermutator. After slightly over a minuteresidence time, the product temperature had dropped to 13° C. Linepressure between the Thermutator and the Stephan Comminutor was between40 psi and 45 psi. The Stephan Comminutor was operated at about 2960rpm, and product exited the Comminutor at about 20° C. at a linepressure of 25 psi. The pressure was maintained in known manner using acommercial compensator. The produce was then passed to a Benhil Model8345 printer and printed as 1/4 pound blocks. The final product wasdescribed as smooth and showed no evidence of free surface moisture.

EXAMPLE 5

285.28 Kilograms of buttermilk containing 28.21% total solids, 1.72% fatwas admixed with 5.94 kilograms of water and the admixture waspasteurized a 71° C. for thirty minutes. 1.9 Kilograms of salt wereadded to this admixture.

625 kilograms of butter comprising 80% fat, 1.28% solids not fat and1.9% salt were worked in a butter reworker to about 14° C. The butterwas passed to a Cherry Burrell Round Processor Model WTC and heated tobetween 32° C. and 37° C. The buttermilk admixture was added to themelted butter at approximately the same temperature to produce a finaladmixture of 918.01 kilograms containing 65.6% total solids and 55%butterfat and 1.8% salt. The admixture was passed at 36° C. and 15 psito the Gaulin Homogenizer which in turn delivered 2350 pounds per hourat between 100 psi and 160 psi to the Cherry Burrell Thermutator. Bothlegs of the Thermutator were used to pre-crystallize the fat whichdropped in temperature to about 13° C. to 14° C. after approximately 2.5minutes residence. The line pressure intermediate, thepre-crystallization apparatus and the Stephan Comminutor was between 80psi and 110 psi. The Comminutor was operated at 2960 rpm and the productexited the Comminutor at between 20 psi and 30 psi. The produce was thenpassed to a Benhil Model 8345 printer and printed as 1/4 pound blocks.The resulting fat reduced product was smooth and showed no evidence offree surface water.

EXAMPLE 6

426.79 Kilograms of buttermilk comprising 25.02% total solids and 1.48%fat was admixed with 96.82 kilograms of water and the admixture waspasteurized at 71° C. for thirty minutes. 60.04 Kilograms of salt wereadded to the admixture.

475 Kilograms of butter substantially as hereinbefore described, andcontaining 80% fat, 1.5% solids not fat and 1.9% salt was reworked in abutter reworker to 14° centigrade. The cutter was then passed to aCherry Burrell Round Processor Model WTC and heated to between 32° C.and 37° C. The buttermilk and butter were then admixed to produce1004.63 kilograms of a mixture having 50.71% total solids, 38.5%butterfat, and 1.5% salt. The mixture was then pumped at 36° C. and 10psi to a Gaulin Homogenizer operating at a through put of 2350 poundsper hour and generating line pressures of 30 psi to 50 psi. The productwas passed to a Cherry Burrell Thermutator and after a little over aminute residence time had a product temperature of 13° C. Line pressureintermediate the pre-crystallization apparatus and the StephanComminutor was 25 psi to 45 psi. The Stephan Comminutor was operated at2960 rpm and product exiting the Comminutor did so at 20° C. and 15 psito 30 psi. The product was passed to a Benhil Model 8345 printer andprinted as 1/4 pound blocks to produce a smooth, low-fat butter productwithout any substantial amount of free surface water.

We claim:
 1. A process for producing an edible fat-reduced spread of thewater-in-oil type comprising:a) heating fat which at room temperature isnormally solid and contains meltable fat crystals with differing thermalstabilities to below the heat of fusion of the most thermally stablecrystals in the fat for a period of time and to a temperature sufficientto melt a substantial proportion of less thermally stable crystals inthe fat; b) homogeneously admixing sufficient water to the heated fat toreduce the proportion of fat in the resulting admixture to between 30%and 75% by weight; c) cooling the admixture to crystallize a substantialproportion of the uncrystallized fat to increase the solids level andincrease the viscosity of the admixture to produce a pumpable plasticmass; d) feeding the pumpable plastic mass into a turbine-likecomminuting device in which the plastic mass passes through an inletinto a comminuting chamber containing closely-spaced relatively-rotatingconcentric inner and outer rings of spaced blades to cause the plasticmass to pass through the rings of blades and between the blades thereofso as to be cut and mixed thereby and then passed to an outlet; and, e)the increase in temperature of the plastic mass caused by said cuttingand mixing being from about 1.5 Celsius degrees up to a temperatureabove which the plastic mass becomes destabilized and substantialamounts of water are released from the plastic mass.
 2. The process ofclaim 1 wherein the increase in the temperature of the plastic mass dueto the cutting and mixing thereof is between about 1.5 Celsius degreesand 20 Celsius degrees.
 3. The process of claim 2 wherein the increasein the temperature of the plastic mass due to the cutting and mixingthereof is between about 1.5 Celsius degrees and 10 Celsius degrees. 4.The process of claim 3 wherein the increase in the temperature of theplastic mass due to the cutting and mixing thereof is between about 2and 8 Celsius degrees.
 5. The process of claim 1 wherein the fat isselected from the group consisting of butter, renovated butter, andbutter oil.
 6. The process of claim 5 wherein the fat is butter.
 7. Theprocess of claim 6 wherein the butter comprises not less than 80% byweight of milk fat.
 8. The process according to claim 7 wherein thebutter comprises about 80% milk fat, 16% moisture, about 2% milk solidsnot fat, and up to about 2% salt.
 9. The process according to claim 1wherein the fat-reduced spread comprises between 30% and 75% fat as aproportion of the total weight of the admixture.
 10. The processaccording to claim 9 wherein the fat-reduced spread is a low-fat spreadcomprising between 30% and 50% fat as a proportion of the total weightof the admixture.
 11. The process according to claim 10 wherein thelow-fat spread comprises between 35% and 40% fat as a proportion of thetotal weight of the admixture.
 12. The process of claim 1 wherein theadmixture is cooled in step (c) to a temperature in the range of 13° C.to 17° C., with penetrometer values of between 210 and
 360. 13. Theprocess according to claim 12 wherein the admixture is cooled to atemperature of between 14.5° C. and 16.5° C.
 14. The process accordingto claim 13 wherein the admixture is cooled to a temperature of between14.5° C. and 15.5° C.
 15. The process according to claim 1 wherein thetemperature of the pumpable plastic mass upon cutting and mixing is 15°C. to 18.5° C.
 16. The process according to claim 15 wherein thetemperature of the plastic mass upon cutting and mixing is between 15.5°-C. and 16.5° C.
 17. The process according to claim 15 wherein uponcutting and mixing the plastic mass has a penetrometer value between 230and
 270. 18. The process according to claim 1 wherein the temperaturerise of the plastic mass due to mixing alone is about 1° C.